From f2f4d364ee9e3012e44591a620ce1177004d1165 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@juliahub.com>
Date: Wed, 8 Apr 2026 14:36:01 +0530
Subject: [PATCH] fix: allow multiple observables to solve from the same inline
 linsolve index

---
 .../src/ModelingToolkitTearing.jl                     | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/lib/ModelingToolkitTearing/src/ModelingToolkitTearing.jl b/lib/ModelingToolkitTearing/src/ModelingToolkitTearing.jl
index 6768bd1..40c8588 100644
--- a/lib/ModelingToolkitTearing/src/ModelingToolkitTearing.jl
+++ b/lib/ModelingToolkitTearing/src/ModelingToolkitTearing.jl
@@ -159,8 +159,8 @@ function MTKBase.unhack_system(sys::System)
     subst = SU.Substituter{false}(additional_subs, SU.default_substitute_filter)
     obseqs = obseqs[obs_mask]
     map!(subst, obseqs, obseqs)
-    map!(subst, additional_eqs, additional_eqs)
     append!(eqs, additional_eqs)
+    map!(subst, eqs, eqs)
 
     if sched isa MTKBase.Schedule
         map!(subst, values(sched.dummy_sub))
@@ -190,14 +190,7 @@ function populate_inline_scc_map!(
     is_ldiv || return
     len = length(ldiv)
     buffer = get!(() -> zeros(Int, len), inline_linear_scc_map, ldiv)
-    if !iszero(buffer[idx])
-        is_diffeq && return
-        throw(ArgumentError("""
-        Found multiple inline linear solves solving the same variable. \
-        This should not be possible. Please open an issue in \
-        `ModelingToolkit.jl` with an MWE.
-        """))
-    end
+    iszero(buffer[idx]) || return
     buffer[idx] = ifelse(is_diffeq, -eq_i, eq_i)
 end